Stabilized aluminosilicate hydrocracking catalyst

ABSTRACT

A process is described for producing gasoline from a paraffinic hydrocarbon feed wherein the feed is catalytically cracked and then reformed. In the process a novel porous hydrocracking catalyst composite is employed. This catalyst comprises a silica-alumina cracking base component and a noble metal hydrogenation component. It is stabilized as a result of a unique method used for introducing the noble metal in the form of a highly dispersed gravimetric precipitate into a gelatinous silica-alumina cogel precursor of the cracking base component. An organic gravimetric reagent is used for the precipitation. The resulting crackate is reformed by ordinary methods.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. application Ser.No. 769,625, filed Feb. 16, 1977 U.S. Pat. No. 4,137,146, which is acontinuation-in-part of U.S. application Ser. No. 586,674, filed June13, 1975 and now abandoned.

BACKGROUND OF THE INVENTION

1. Field

The present invention is concerned with the production of reformedcracked gasoline in a combination process employing catalytichydrocracking and catalytic reforming stages. A novel stabilizedcatalyst containing a silica-alumina cracking base component is employedin the catalytic cracking stage. The cracking base component is of thesimultaneously coprecipitated cogel-type.

2. Prior Art

The prior art abounds with methods for the production of catalystscomprising a metal associated with the surface of a porous inorganicoxide support. In accordance with the prior art, said catalyst can beproduced in a variety of ways, for example by impregnating a preformedinorganic oxide carrier with the metal or by coprecipitating the metalas an oxide or hydroxide along with the materials forming the porousinorganic oxide support; for example, the pH of a solution containingdissolved silica, alumina and palladium can be adjusted to the pointwhere the silica and alumina coprecipitate and the palladium ischemisorbed to a limited extent onto the resulting silica-aluminacoprecipitate, said palladium being primarily in the form of solublepalladium hydroxide and/or palladium salts. The palladium does notcoprecipitate along with the silica and alumina, since the palladiumcation and, more particularly, palladium hydroxide, are soluble at pH'swithin the range that silica and alumina coprecipitate.

The preparation of cogelled silica-alumina cracking catalyst basecomponents and catalytic cracking components by simultaneousprecipitation is described in U.S. Pat. No. 3,280,040.

U.S. Pat. No. 2,662,861 teaches preparing: (1) a slurry of alumina,washing it, adding a promoter, bubbling hydrogen sulfide through (2) asolution of chloroplatinic acid hexahydrate, mixing (1) and (2) togetherand drying to form a catalyst. A similar process is disclosed in U.S.Pat. No. 3,617,509.

U.S. Pat. No. 2,898,305 teaches mixing silica in a slurry form with aninsoluble inorganic compound, drying and calcining.

U.S. Pat. No. 2,688,603 teaches catalyst preparation by distributing anorganic compound containing a potentially catalytically active metal onthe surface of a suitable support and decomposing the organic portion ofthe molecule.

U.S. Pat. No. 3,210,296 teaches impregnating an inorganic oxide supportby use of a noble metal compound dissolved in an alcohol, ether,aldehyde, ketone, or mixtures thereof.

U.S. Pat. No. 3,801,515 teaches preparing a finely divided metal byreducing a metal-containing compound in an aqueous medium and intimatelyintermixing the metal with a gelatinous precipitate. It has beensurprisingly discovered that when catalysts comprising a noble metal ofGroup VIII associated with a porous inorganic oxide support are preparedby the method of the present invention, a larger proportion of themetal, preferably palladium, attempted to be incorporated into saidcatalysts is actually incorporated therein than is obtained by the priorart coprecipitation-plus-chemisorption method of catalyst preparation.It has also been surprisingly discovered that when a catalyst isprepared according to the present invention the resulting catalystexhibits exceptional catalytic hydrogenation stability. It is believedthat the high catalytic hydrogenation stability found for the catalystprepared in accordance with the present invention is the result of amore uniform and possibly more specific dispersion of the metal upon thesurface of the porous inorganic oxide support than is ordinarilyobtained.

SUMMARY OF THE INVENTION

In accordance with the present invention, an improved process isprovided for the production of a product comprising reformed crackedgasoline from a substantially paraffinic hydrocarbon feed by stepscomprising hydrocracking and reforming wherein the hydrocracking iscarried out under ordinary hydrocracking conditions by contacing thefeed with a substantially porous hydrocracking catalyst composite, saidcomposite comprising an amorphous simultaneously cogelled silica-aluminacracking base component and at least one catalytic hydrogenationcomponent selected from the group consisting of noble elements of GroupVIII of the Periodic Chart of the Atoms, said elements being present insaid composite in at least one form selected from the group consistingof oxides and sulfides and the metal, thereby producing a hydrocarbonhydrocrackate; said reforming being effected by contacting at least asubstantial portion of said hydrocracking with an ordinary reformingcatalyst under ordinary catalytic reforming conditions, therebyproducing said gasoline products, the improvement comprising carryingout said hydrocracking using a stabilized catalytic cracking composite,said stabilization being obtained by admixing an organic-metal compoundprecipitate with a freshly prepared gelatinous silica-alumina precursorof said cogelled cracking base component, said precipitate resultingfrom the interaction, by complex compound formation or metathesis, of awater-soluble compound of at least one of said elements with at leastone organic gravimetric reagent therefor, said reagent and compoundexhibiting a solubility product, Ksp, of less than about 10⁻³ ; andconverting the resulting mixture into said stabilized catalyst, saidconverting comprising at least a step of calcining by maintaining saidresulting mixture at a temperature in the range of from about 500° F. to1800° F. for a period sufficient for expelling volatile portions of themixture and in the range of from about 1 to 48 hours.

Other aspects of the invention include the aforementioned processwherein:

(A) (a) the cracking base component is at least 80 weight percentamorphous silica-alumina of which the alumina content is in the rangefrom about 30 to 98 weight percent and the balance of said cracking basecomponent comprises at least one inorganic refractory oxide selectedfrom the group consisting of oxides of Group II and of the otherrefractory oxides of Groups III and IV;

(b) the hydrocracking catalyst composite has a surface area in the rangefrom about 50 to 700 m² /gram;

(c) the hydrogenation component is selected from the group consisting ofplatinum and palladium;

(d) the solubility product, Ksp, is less than about 10⁻⁵ ; and

(e) the hydrocrackable hydrocarbon feed contains at least a 20 volumepercent fraction which is heavier than gasoline;

(B) (a) the cracking base component is at least about 90 weight percentamorphous silica-alumina of which the alumina content is in the rangefrom about 40 to 95 weight percent and the balance of said cracking basecomponent comprises at least one inorganic refractory oxide selectedfrom the group of inorganic refractory oxides;

(b) the hydrocracking catalyst composite has a surface area in the rangefrom about 150 to 500 m² /gram; and

(c) the solubility product, Ksp, is less than about 10⁻⁵ ;

(C) the Group VIII element is selected from the group consisting ofplatinum and palladium;

(D) the hydrocrackable feed is a gas oil having a boiling point rangefrom about 400° F. to 1050° F.;

(E) the cracking base component consists essentially of silica andalumina;

(F) the gravimetric reagent is at least one organic compound selectedfrom the group consisting of oximes, azoles, mercaptides and anilides;

(G) the gravimetric reagent is at least one organic compound selectedfrom the group consisting of azoles which contain an aromatic ring andinertly substituted derivatives thereof;

(H) the precipitation of the noble metal compound is effected in situ insaid gelatinous silica-alumina precursor;

(I) there is a further improvement wherein the reforming is carried outusing a stabilized platinum-group-containing reforming catalyst, saidstabilization being obtained by admixing a freshly prepared gelatinousprecipitate selected from the oxides of the metals of Groups II, III andIV with an organic-metal compound precipitate, said organic metalcompound precipitate resulting from the interaction, by complex compoundformation or metathesis of a water-soluble compound of platinum orpalladium with at least one organic gravimetric reagent therefor, saidreagent and compound exhibiting a solubility product, Ksp, of less thanabout 10⁻³ ; and converting the resulting mixture into said stabilizedreforming catalyst, said converting comprising at least a step ofcalcining by maintaining said mixture at a temperature in the range offrom about 500° F. to 1800° F. for a period sufficient for expellingvolatile portions of the mixture and in the range of from about 1 to 48hours; and

(J) the gravimetric agent is 1,2,3-benzotriazole and inertly substitutedderivatives thereof.

Yet further aspects of the invention include:

(A) a composition which is a precursor of the aforementioned stabilizedhydrocracking catalyst; and

(B) other and more particular modifications of the aforementionedinvention which will be evident from the examples and description tofollow.

THE HYDROCRACKING CATALYST COMPOSITE The Cracking Base Component

The catalyst of the present invention may contain any cracking basecomponent obtained by simultaneously coprecipitating silica and aluminafrom an aqueous solution or sol of sodium silicate or silica and of analuminum compound which is a precursor of alumina hydrogel (i.e., whichforms the hydrogel when the pH of the aqueous solution or sol isincreased or decreased). The relative amount of amorphous silica-aluminain the cracking base component should be at least 80 weight percent,more preferably at least 90%, and most preferably should consistessentially thereof. The relative amount of alumina in the amorphoussilica-alumina portion of the cracking base may vary widely and isusually in the range 30 to 98 weight percent (water-free basis),preferably 40 to 95 weight percent. The balance of the cracking basecomponent may be one or more refractory inorganic oxides or combinationsof such oxides of Group II and of the other oxides of Groups III and IV,preferably gel-forming oxides. Typical inorganic oxides that canconstitute said balance are magnesia, zirconia, titania, and mixturesthereof.

The cracking base component and the hydrocracking catalyst compositemust be substantially porous, that is, must contain sufficient pores toprovide a surface area (BET method) of at least about 50 m² /g of thebase or of the catalyst composite. Usually this surface area will be inthe range 50 to 700 (i.e., substantially porous), preferably 150 to 500m² /g.

The Catalytic Hydrogenation Component

One or more of the noble elements of Group VIII provide thehydrogenation component required for the novel hydrocracking catalyst ofthe invention. Preferably the element is platinum or palladium, and mostpreferably is palladium. The hydrogenation component may be present inthe activated catalyst in the oxide, sulfide or metallic form or anycombination thereof. While compounds of these elements may chemisorb tosome extent from their aqueous solution onto or into a gelatinoussilica-alumina precipitate, this effect does not reduce the suitabilityof the noble metal compound for use in the present invention. In thecase of the present noble metals, this chemisoprtion, in general, isincomplete and/or relatively easily reversed. And therein lies a seriousproblem in that the high cost of the noble metals makes any loss acostly loss. In direct contrast, the organic gravimetric reagents hereinform tight organic-metal complex compounds or metathesis products whichprecipitate from an aqueous medium, which do not dissociate readily upondilution and which are for all practical purposes wholly retained in theprecipitated gelatinous silica-alumina precursor of the catalytichydrocracking composite of the present invention. Accordingly,supernatant water may be drained away from the gelatinous precipitatewith little or no loss of the noble metal compound, and otheroperations, including water-washing of the gelatinous composite, dryingof this composite by suction filtration and the like steps may beconveniently carried out, again with little or no loss of the noblemetal, particularly where the Ksp (see discussion below) for thegravimetric reagent-metal compound combination is less than about 10⁻⁵.

In view of their high cost, the amount of noble metals, calculated asmetal, desirably present in the hydrocracking catalyst composite hereinwill be an amount in the range 0.01 to about 3 weight percent of thetotal composite, and more preferably in the range from about 0.02 toabout 1.0 weight percent. When a metal is present in the catalyst in arelatively small amount, it is very desirable that the metal be finelydivided and dispersed as uniformly as possible over the surface, bothinternal and external, of the support. This insures that a greatereffective metal surface area will be present in the catalyst. Theorganic-metal compound precipitates produced in the gravimetricprecipitation herein do not appear to agglomerate or cluster seriously.Accordingly, the precipitated noble metal compound is found to be ratheruniformly distributed throughout the gelatinous silica-aluminaprecipitate in the formation of the composite precipitate which is theprecursor of the hydrocracking catalyst herein.

Metals which promote the activity of the Group VIII noble metals forhydrogenation-dehydrogenation, such as, for example, rhenium,technetium, lead, tin and germanium, may be present in an amount from0.01 to 3 weight percent of the catalytic composite, and more preferablyin the range from about 0.02 to about 1.0 weight percent. Thesepromoters, in general, may also advantageously be incorporated in thecatalyst by the gravimetric precipitation method of the presentinvention.

THE ORGANIC GRAVIMETRIC PRECIPITANT

Organic compounds, in general, suitable for use as gravimetric reagentsfor the noble metal compounds in aqueous media are suitable for use inthe practice of the invention and are contemplated for such use (see"The Analytical Chemistry of the Noble Metals", by F. E. Beamish,Pergamon Press, which is incorporated herein by reference, for extensivedescription re organic gravimetric reagents and their use in noble metalanalysis by precipitation).

Suitable organic gravimetric reagents are, in general, organic compoundswhich have no carbon-metal linkages and have at least a moderatesolubility in water. In their use, the organic compound reacts orinteracts with the noble metal compound by one or more reactionmechanisms including complex-compound formation and metathesis and awater-insoluble compound is formed. Representative reactions are asfollows:

(1) 2 (1,2,3-benzotriazole)+PdCl₂ →PdCl₂ (1,2,3-benzotriazole)₂ ↓complex compound

(2) 2 (o-hydroxyphenyl)benzoxazole+PdCl₂ →Pd(C₁₃ H₃ NO₂)₂ ↓+2 HClmetathesis product

The precipitates produced by the reaction of an organic gravimetricreagent with a noble metal compound as herein are believed to involve,in general, bonding (polar and/or coordinate complex) between the metalcation and one or more nonmetallic (such as oxygen, nitrogen andsulfur), electron-rich constituents of the organic compound. Forconvenience and by definition, these are referred to herein asorganic-metal compounds.

Whether a gravimetric reagent is satisfactory depends upon the desireddegree of precipitation of the metal constituent from the aqueoussolution. In general, the reagent should be one for which the solubilityproduct for an aqueous medium [Ksp, i.e., (molar concentration of theorganic gravimetric compound) (molar concentration of the noblemetal)=Ksp; see "Qualitative Chemical Analysis" by A. A. Noyes, page122] at the precipitation temperature is less than about 10⁻³,preferably less than 10⁻⁵ in the case of the costly metals, for examplethe Group VIII noble metals. In a corollary sense, the foregoing ingeneral requires that a satisfactory organic gravimetric compound have awater solubility of at least about 0.01 molar (a moderate watersolubility) and preferably a solubility of at least about 0.1 molar.

Representative organic gravimetric reagents suitable for use hereininclude:

1,2,3-benzotriazole

nioxime

1,10-phenanthroline

alpha-nitroso-beta-naphthol

2-hydroxy-1-naphthaldehyde

dimethylphenylbenzylammonium chloride

phenylsemicarbazide

phenothiazine

thiourea

2-mercaptobenzothiazole

thiophenol

dimethylglyoxime

alpha-furildioxime

thionalide

thioacetamide

beta-mercaptopropenoic acid

2,3-dimercapto-1-propanol

strychnine sulfate

acridine

2-phenylbenzothiazole

thiobarbituric acid

2-mercaptobenzoxazole

thioacetanilide

ammonium p-aminophenyldithiocarbamate

1-nitroso-2-naphthol

salicyladoxime

benzoylmethylglyoxime

beta-furfuraldoxime

alpha-benzoinoxime oxaldenediamidoxime

2-thiophenetransaldoxime

2-o-hydroxyphenylbenzoxazole

N-phenyl-N-phenylazohydroxylamine

6-nitroquinoline

5-methyl-8-hydroxyquinoline

quinaldinic acid

quinolinic acid

beta-aminopicolinic acid

alpha-picolinic acid

peaselenol

1,3-dimethyl-4-imino-5-hydroxyimino alloxan

alpha,beta-bis(hydroximino)acetoaceto-o-toluidide

3-hydroxy-1-(p-tolyl)-3-phenyltriazine

p-thiocyanatoaniline

p-aminosalicylic acid

p-aminoacetophenone phthalinilic acid

1-naphthylphthalanilic acid

p-tolyphthalanic acid

o-carboxyisonitrosoacetanilide

alpha,beta-dioximidoacetoacetanilide

2-mercaptobenzimidazole

phenylthiohydantoic acid

diethyldithiophosphoric acid

and the like organic gravimetric reagents. Of the particular classes oforganic gravimetric reagents, the oximes, azoles, mercaptides andanilides, the azoles are preferred for use herein. Of the latter, theazoles which contain an aromatic ring, for example 1,2,3-benzotriazoleand the like, and the inertly substituted derivatives thereof, are mostpreferred, particularly for use with Group VIII noble metals, because ofthe efficient precipitation of these metals by them. By "inert," havingreference to substituents, is meant a substituent which does not causereduction to the metal of the catalytic metal constituent of the noblemetal compound. The precipitation of a noble metal compound in anaqueous medium by an organic gravimetric reagent is conventional inanalytic chemistry, and it is to be understood that this practice ofitself is not the gist of the present invention.

THE GELATINOUS PRECIPITATE

The preparation of gelatinous precipitates comprising alumina andsilica, i.e., silica-alumina precipitates, by simultaneouscoprecipitation of hydrogel-forming compounds of silicon and aluminumfrom a common solution or sol is known and described in the art (see,for example, U.S. Pat. No. 3,280,040).

It is essential to the practice of the invention that the inorganicoxide gelatinous precipitate be freshly prepared. If the inorganicgelatinous precipitate is allowed to age for a time before theorganic-metal compound is formed therein and is intimately intermixedtherewith, an inferior catalyst will result. While not wishing to bebound to this explanation, it is believed that longer delays allow thegelatinous precipitate to further set up, forming "cross-links," whichforestall uniform distribution of the precipitated metal compound in thegelatinous precipitate and ultimately on all the surfaces of thesupport. Usually the delay should be no more than about 2 hours, andpreferably there should be no more than a 1-hour delay between theformation of the gelatinous precipitate and the incorporation of thenoble metal into the gelatinous precipitate.

The incorporation of the organic-metal compound of the noble metal intothe gelatinous precipitate may be accomplished in any suitable way, forexample by:

(1) in situ formation of the organic-metal compound precipitate of thenoble metal compound in a preformed gelatinous precipitate;

(2) simultaneous and in situ formation of the gelatinous precipitate andof the organic-metal compound precipitate; and

(3) formation separately of the aforementioned precipitates andthereafter intermixing them.

Method (1) is a preferred method. Thus, in this case, the suitability ofthe gel formation is assured before the costly noble metal component iscommitted to the mix. Where the suitability of the precursor materialsis assured, for example by a prior test or experience, method (2) isthen particularly preferred.

The intimate intermixing is preferably accomplished as follows: anaqueous medium is formulated comprising: (1) dissolved precursors of thegelatinous precipitate: and (2) dissolved noble metal compound. The pHof the solution is adjusted by the addition of base or acid theretountil the gelatinous precipitate results. An organic precipitating agentis then added, for example a benzotriazole, to the aqueous slurry of thefreshly prepared inorganic oxide gelatinous precipitate while agitatingthe slurry to precipitate the dissolved metal as finely dividedorganic-metal compound. In large part, this precipitate is formed insitu in the aqueous gel (hydrogel) and the balance, if any, issubstantially (at least about 95% efficient) incorporated into the gelby the intimate intermixing.

While it is preferred that the gelatinous precipitate be formed prior toor concurrently with the precipitation of the organic-metal compound,the method of manufacturing a catalyst of the present invention can becarried out by first precipitating the organic-metal compound followedby precipitation of the inorganic oxide or precursor thereof. It may inthis situation be desirable in some cases to stabilize the finelydivided organic-metal compound to inhibit any tendency of the particlesto agglomerate by use of suitable stabilizers such as casein,polyacrylic acid, and the like.

The term "intimately intermixing" is used to mean that the finelydivided organic metal compound is uniformly distributed on the surfaceof the fresh inorganic oxide gelatinous precipitate. Generally, it isquite desirable that agitation take place to more completely accomplishthe intimate intermixing. The agitation may be continuous orintermittent.

Once the finely divided organic-metal compound has been intimatelyintermixed with the fresh inorganic oxide gelatinous precipitate, theresulting mixture may then be treated by conventional methods to formcatalyst particles of a practical and useful size. Thus, this mixture isa novel composition, a catalyst precursor, which is useful for thepreparation of a novel hydrocracking catalyst composite, which may becharacterized as follows:

(1) a silica-alumina component having an alumina content, calculated onthe basis of the respective oxides, in the range from about 40 to 95weight percent;

(2) a Group VIII noble metal organic-metal compound content, calculatedas the metal and based upon said silica-alumina content, the lattercalculated as the oxides, in the range from about 0.1 to 3 weightpercent; and

(3) a residue comprising water, resulting water-soluble inorganic salts,and a minor amount of the organic gravimetric reagent.

Generally, the intermixed organic-metal compound-gelatinous precipitateis water-washed or ion-exchanged to remove soluble components, formedinto particles, as for example by extruding or the like, and theparticles are then heated to a temperature within the range from about500° to about 1800° F. for from about 1 hour to about 48 hours. Theheating serves to decompose the organic residue. The heating willfurther serve to calcine and activate the catalytic composite.Preferably, for the hydrocracking catalysts herein, the heating willtake place at a temperature within the range from about 950° F. to about1800° F. for from about 2 hours to about 8 hours.

The product produced in accordance with the present invention will,after the heating step, preferably exhibit a parameter consisting of theproduct of the bulk density in grams per cc of the particles and thesurface area in square meters per gram which falls within the range fromabout 100 m² /cc to about 500 m² /cc, and more preferably, especiallywhen the catalyst is a hydrocracking catalyst, within the range fromabout 200 m² /cc to about 500 m² /cc.

HYDROCRACKING STAGE The Feed

The novel stabilized catalytic cracking composite of the presentinvention is suitable for use in converting substantially paraffinic(less than 10 volume percent aromatic hydrocarbon content)hydrocrackable hydrocarbon feeds under conventional hydrocrackingconditions, and these feeds and conditions are contemplated for useherein. Preferably the organic nitrogen content of the hydrocarbonfeedstocks should be below about 0.05 weight percent, more preferablybelow about 0.02 weight percent, and most preferably below about 10 ppm.The organic sulfur content of the feedstocks also should be below about0.05 weight percent, preferably below about 0.02 weight percent, andmore preferably below about 10 ppm. If desired, the hydrocarbonfeedstocks may be subjected to a conventional hydrofining pretreatmentstep prior to being converted in the presence of the catalyst of thepresent invention. The hydrocrackable hydrocarbon feeds particularlycontemplated for use herein vary over a wide range and are petroleumdistillates having boiling-point ranges in the range from about 325° F.to about 1050° F. and higher and which contain a substantial (aboveabout 20 volume percent) fraction which is heavier than gasoline, i.e.,boils above about 383° F. Representative suitable hydrocrackablehydrocarbon feeds include naphthas, kerosene distillates, gas oils,vacuum gas oils, heavy vacuum gas oils, cycle oils, recycle oils,mixtures thereof, and the like having an aromatic content of less thanabout 10 volume percent. These feeds may be obtained as all or a portionor the product stream from straight runs, thermal cracking, catalyticcracking and the like hydrocarbon processing operations using feedsderived from petroleum, gilsonite, shale, coal tar and the like sources.Prior to use as feeds for the hydrocracking stage herein, theaforementioned feeds may also have been subjected to one or moreprocessing steps including desulfurization, demetallation anddenitrification. Preferably the feed is a vacuum gas oil having aboiling point (ASTM-D1160) in the range from about 400° F. to about1050° F., more preferably from about 500° F. to about 950° F.

The Conditions

The hydrocracking process conditions herein may be ordinaryhydrocracking conditions, for example a temperature within the rangefrom about 450° F. to about 850° F., a pressure within the range fromabout 500 psig to about 3500 psig, a liquid hourly space velocity withinthe range from about 0.5 to about 3.0, and a total hydrogen rate withinthe range from about 1000 SCF to about 20,000 SCF, preferably from about2000 SCF to about 10,000 SCF, of hydrogen per barrel of feedstock.

When the catalyst is contacted with the hydrogen used in a hydrocrackingreaction, some reduction to metal of any metal oxides that are presentwill take place. This is not detrimental, and in fact is necessary todevelop the ordinary catalytic hydrogenation activity of the catalyst,so long as the hydrogen does not contact the catalyst at a temperatureappreciably higher than the reaction temperature at the start of therun, i.e., a temperature high enough to cause sintering of the metal onthe catalyst with concurrent metal surface area reduction.

Reforming Stage

Ordinary reforming conditions and catalysts are contemplated for use inthe invention, including the use of a conventional reforming catalystwhich comprises at least one refractory oxide and a metal componentselected from the group consisting of the metals and compounds of themetals in the platinum group, preferably in a hydroforming stage whereinlow-pressure hydroforming conditions are employed (see, for example,U.S. Pat. No. 3,415,737 and the references cited therein). In a furtherpreferred embodiment, the hydrocracking catalytic composite and thereforming catalyst are both prepared using an organic gravimetricprecipitating reagent as herein for the incorporation of the noble metalinto a gelatinous metal (Groups II, III and IV) oxide (hydrogel)precipitate which is a precursor to the respective hydrocracking orreforming catalyst.

The Feed

At least a substantial (at least 25 volume percent thereof) portion ofthe feed to the reforming stage will comprise all or any suitablereformable fraction of the hydrocrackate effluent from the hydrocrackingstage of the present invention. The balance of the feed, if any, maycomprise a reformable (i.e., paraffinic and/or naphthenic hydrocarbonswhich contain at least 6 carbon atoms per molecule) hydrocarbon fractionhaving a boiling-point range in the range from about 75° F. to 450° F.,for example a suitable refinery stream. Preferably the total feed to thereforming stage has a boiling-point range in the range 75° F. to 450° F.and has an aromatic hydrocarbon content which constitutes less thanabout 10 volume percent of the feed.

The Catalyst

Platinum-group-containing reforming catalysts comprising a platinumgroup component and at least one refractory oxide of elements of GroupsII, III and IV oxides, preferably consisting essentially of alumina, anda halogen component are contemplated for use herein and are well knownin the art, except in the case of those catalysts wherein the metal isgravimetrically incorporated into an otherwise conventional catalystcomposite by the novel method described above. As used herein and bydefinition, by the term "ordinary noble-metal-containing reformingcatalyst" is meant the aforedescribed conventional reforming catalysts.The platinum-group component of these reforming catalysts is present inone or more of the metal, metal oxide, metal sulfide and metal halideforms. In addition to the platinum group metal, and as conventional inthe art, one or more promoter components may also be present in thereforming catalyst, for example a rhenium and/or tin component, whichmay also be present in one or more of the aforementioned forms.

Reforming Process Conditions

Ordinary reforming conditions are contemplated for use in the presentinvention and in general include a temperature in the range 700°-1000°F., a pressure in the range 50 to 1000 psig, a hydrogengas-to-hydrocarbon mol ratio in the range 1:1 to 10:1, and a liquidhourly space velocity, volume of feed per volume of catalyst (LHSV), inthe range from 0.2 to 10. For the preferred low-pressure conditionsherein, a temperature in the range 880°-975° F., a total pressure in therange 75 to 500 psig (partial pressure of H₂ of 60 to 80% of totalpressure), a hydrogen gas-to-feed mol ratio in the range 1-10, and anLHSV in the range 0.75 to 5.0 are contemplated for use with aplatinum-rhenium-alumina reforming catalyst composite. The resultinggasoline reformate has an excellent octane number (F-1 Clear) in therange 80 to 110.

EXAMPLES

The invention will be better understood with reference to theillustrative examples which follow.

EXAMPLE 1 Prior Art Catalyst

A silica-alumina cogel was made following the general procedure setforth below.

1130 g of AlCl₃ 6H₂ O were dissolved in 5 liters of H₂ O, and 125 ml ofglacial acetic acid were added to form a first solution. 450 g of sodiumsilicate were dissolved in 2.5 liters of water to form a secondsolution. Said first and second solutions were combined to form amixture, the pH of which was adjusted to 6.5 by the addition of 3 litersof a solution of 2 parts of H₂ O and 1 part NH₄ OH. The resultingmixture, in the form of a suspension, was heated to 150° F., the pH wasreadjusted to 6.5, and the mixture was filtered to produce a cogel pastefilter cake. The filter cake was dried at 95° F. to a solids content of30%. The solids were washed 4 times in about 10 liters of 1% ammoniumacetate solution at 150° F. The washed gel was contacted with a solutioncontaining 0.66 g palladium tetraammine dinitrate in 570 ml of water forabout 1 hour. The solution was removed and the cogel, in 10-16 meshform, was dried and a portion was calcined in substantially dry air for4 hours at 450° F., 8 hours at 1000° F. and 4 hours at 1400° F.

This catalyst was used to hydrocrack a feedstock having thecharacteristics set forth in Table I below.

                  TABLE I                                                         ______________________________________                                        ASTM D-1160 Boiling Range, °F.                                         Start                     553                                                  5%                       589                                                 10%                       595                                                 30%                       617                                                 50%                       646                                                 70%                       684                                                 90%                       732                                                 95%                       763                                                 End                       859                                                 ______________________________________                                        Other characteristics:                                                        Gravity, API              39.9                                                Aniline point, °F. 192.7                                               Sulfur, ppm               1-2                                                 Nitrogen, ppm             0.1                                                 Pour point, °F.    +55                                                 Paraffins + naphthenes, vol. %                                                                          90                                                  Aromatics, vol. %         10                                                  ______________________________________                                    

The feedstock was hydrocracked in a recyle run under these conditions:

    ______________________________________                                        Total pressure, psig    1200                                                  Liquid hourly space velocity, V/V/hr.                                                                 4.0                                                   Conversion, liquid vol. % to 550° F.                                                           60                                                    Recycle gas rate, SCF/bbl. of feed                                                                    5600                                                  Boiling range of liquid product recycled                                                              550° F.+                                       ______________________________________                                    

Catalyst inspections and test results are shown in Table II.

EXAMPLE 2 A Catalyst of the Present Invention

A catalyst in accordance with the present invention in which palladiumis precipitated as an organic-metal compound was made as follows (allparts by weight unless otherwise specified):

Solution A was 483 parts water, 100 parts glacial acetic acid and 1295parts of an aluminum chloride solution containing 4.9 weight percentaluminum. Solution B was 278 parts sodium silicate solution (containing28.7 weight percent SiO₂) and 1000 parts water. Solution B was combinedwith Solution A slowly, with rapid stirring. A clear solution results.

The combined solution was titrated to a pH of 6.0 with a solution of 3volumes of water to one volume concentrated NH₄ OH, forming a gelatinousprecipitate.

A solution containing 0.441 parts palladium as dissolved Pd(NO₃)₂ and[Pd(NH₃)₄ ](NO₃)₂ in about 8 parts water was added to the gel. Themixture was stirred rapidly for about 15 minutes to insure that thepalladium was uniformly dispersed throughout the gel. Then added to thegel were about 83 parts water containing 1.49 parts of dissolved1,2,3-benzotriazole. Addition of the dissolved palladium salt and thebenzotriazole was completed within about 40 minutes after the completionof the gel precipitation step. The mixture was stirred rapidly for 15-20minutes to insure that the benzotriazole was uniformly dispersedthroughout the gel. The benzotriazole reacted with the palladium salt toform an insoluble organic-metal compound.

After 11/2 hours aging, the slurry was heated to 140° F., the pHadjusted to 6.4, and the slurry was filtered and partially dried toabout 70% volatiles content. 17.6 parts of this cake were formed andexchanged 5 times for 1/2 hours at 150° F. in about 55 parts of watercontaining 1 weight percent ammonium acetate and having a pH of 6.0.After the exchange, the catalyst was washed once in water and partiallydried to a volatiles content of 32.5 weight percent. This material wascalcined in substantially dry air for 31/2 hours at 400° F., 5 hours at950° F., and 2 hours at 1400° F. to produce the finished catalyst.

The first filtrate contained 0.4-0.5 ppm palladium. About 3250 parts offiltrate were produced, which therefore contained about 0.0013 to 0.0016parts of palladium. Thus, over 99.5% of the palladium added remainedwith the filter cake. Analysis of the final catalyst confirmed thatessentially all the added palladium is in the finished catalyst.

This catalyst was tested using the same feed and test conditions asExample 1. Catalyst inspections and test results are shown in Table II.

The run length obtained with this catalyst was 50% greater than obtainedwith a comparable prior art catalyst. This was accomplished withoutsacrificing product selectivity. In addition, the hydrogenationcomponent was added during the normal production of the silica-aluminacomponent, thereby eliminating the need for the costly steps associatedwith impregnation of the hydrogenation component.

                  TABLE II                                                        ______________________________________                                                            Example No.                                                                     1       2                                               ______________________________________                                        Palladium content (wt. %)                                                                           0.24      0.24                                          Bulk density, grams/cc                                                                              0.86      0.89                                          Surface area, m.sup.2 /gram                                                                         363       345                                           Final calcination temperature, °F.                                                           1400      1400                                          Run length (hours to 680° F.)                                                                380       570                                           C.sub.5 + liquid vol. %                                                                             105.6     105.4                                         C.sub.5 + wt. % yield at 640°-650° F. hydro-                    cracking temperature  93.5      93.6                                          250°- liquid vol. % yield at 640°--650° F.               hydrocracking temperature                                                                           64.3      64.9                                          ______________________________________                                    

As in the above example, it is usually more desirable that the metalcompound be intimately intermixed into the gelatinous precipitatefollowed by the introduction of the organic gravimetric reagent and theensuing precipitation of the organic-metal compound. The order of theintroduction of the reactants, the soluble metal compound and theorganic gravimetric reagent may also be reversed. In this event, thegravimetric reagent is intimately admixed with the gel, is incorporatedin substantial part therein; and then the water-soluble noble metal islikewise incorporated into the gel. Again, the desired insolubleorganic-metal compound, complex compound and/or unsoluble metathesisproduct, is formed substantially in situ in the gelatinous precipitateand a useful catalyst precursor is produced. It will be clear in view ofthe foregoing description and examples that in general the presentmethod is an improved and effective means for producing catalysts whichcontain a noble metal component.

It will also be clear that the present invention provides new and usefulprecursors for the production of new and improved catalytichydrocracking catalyst composites and catalytic reforming catalystcomposites in which the noble metal catalytic component of therespective catalyst is stabilized by the gravimetric precipitationmethod described above. Further, in view of the foregoing, it will beclear that the present invention provides a new and advantageouscombination hydrocracking-hydroforming process.

It is apparent that many widely different embodiments of this inventionmay be made without departing from the scope and spirit thereof; and,therefore, it is not intended to be limited except as indicated in theappended claims.

What is claimed is:
 1. A composition suitable for use as a catalystprecursor which comprises:(1) an amorphous silica-alumina componenthaving an alumina content, calculated on the basis of the respectiveoxides in the anhydrous form, in the range from about 40 to 95 weightpercent, said silica-alumina having been simultaneously cogelled; (2) aGroup VIII noble metal organic-metal compound component having a noblemetal content, calculated as the metal and based upon saidsilica-alumina content, in the range from about 0.1 to 3 weight percent,said organic-metal noble metal compound component, a precipitate, havingbeen produced by the interaction by complex compound formation ormetathesis in aqueous medium of a water-soluble compound of at least oneof said noble metals with at least one organic gravimetric reagenttherefor, said reagent and compound exhibiting a solubility product,Ksp, of less than about 10⁻³ ; and (3) a residue comprising water,water-soluble inorganic salts resulting from said cogelation and saidinteraction, and a minor amount of said reagent.
 2. A composition as inclaim 1 wherein said gravimetric reagent is selected from the groupconsisting of oximes, azoles, mercaptides and anilides.
 3. A compositionas in claim 1 wherein said gravimetric reagent is selected from thegroup consisting of 1,2,3-benzotriazole and inertly substitutedderivatives thereof.